I cried during various arcs in one piece, first time would be when nami is asking luffy for help in the cocoyashi arc early on, that is just tear breaking. Nami is so cute.After that, chopper's flashback is tearbreaking for me as well. And during the arabasta arc when they leave at the end, and they all show their X on the arms, made me really happy and a few happy tears came.

So, all in all, one piece is really emotional and awesome and i do get teary quite a lot.